Bug 27680: Allow traditional multi-params to work

This patch allows the preceeding test to pass. Strictly, we want a comma
delimited string for our _order_by parameter, but we cannot easily block
a traditional multi-passed parameter.  As such the 'nice' thing to do is
handle it when such a thing is passed as it will pass through validation
regardless.

Signed-off-by: Tomas Cohen Arazi <tomascohen@theke.io>

Signed-off-by: Jonathan Druart <jonathan.druart@bugs.koha-community.org>

Signed-off-by: Jonathan Druart <jonathan.druart@bugs.koha-community.org>

Koha/REST/Plugin/Query.pm

@@ -92,7 +92,7 @@ Generates the DBIC order_by attributes based on I<$params>, and merges into I<$a
 
             if ( defined $args->{params}->{_order_by} ) {
                 my $order_by = $args->{params}->{_order_by};
-                $order_by = [ split(/,/, $order_by) ] if ( index(',',$order_by) == -1);
+                $order_by = [ split(/,/, $order_by) ] if ( !reftype($order_by) && index(',',$order_by) == -1);
                 if ( reftype($order_by) and reftype($order_by) eq 'ARRAY' ) {
                     my @order_by = map { _build_order_atom({ string => $_, result_set => $result_set }) }
                                 @{ $order_by };